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  2. Purple Earth hypothesis - Wikipedia

    en.wikipedia.org/wiki/Purple_Earth_hypothesis

    The Purple Earth Hypothesis (PEH) is an astrobiological hypothesis, first proposed by molecular biologist Shiladitya DasSarma in 2007, [1] that the earliest photosynthetic life forms of Early Earth were based on the simpler molecule retinal rather than the more complex porphyrin-based chlorophyll, making the surface biosphere appear purplish ...

  3. On Colors - Wikipedia

    en.wikipedia.org/wiki/On_Colors

    On Colors (Greek Περὶ χρωμάτων; Latin De Coloribus) is a treatise attributed to Aristotle [1] but sometimes ascribed to Theophrastus or Strato.The work outlines the theory that all colors (yellow, red, purple, blue, and green) are derived from mixtures of black and white.

  4. Color theory - Wikipedia

    en.wikipedia.org/wiki/Color_theory

    Color theory, or more specifically traditional color theory, is a historical body of knowledge describing the behavior of colors, namely in color mixing, color contrast effects, color harmony, color schemes and color symbolism. [1] Modern color theory is generally referred to as color science.

  5. Rare Earth: Why Complex Life Is Uncommon in the Universe

    en.wikipedia.org/wiki/Rare_Earth:_Why_Complex...

    Rare Earth was succeeded in 2003 by the follow-on book The Life and Death of Planet Earth: How the New Science of Astrobiology Charts the Ultimate Fate of our World, also by Ward and Brownlee, which talks about the Earth's long-term future and eventual demise under a warming and expanding Sun, showing readers the concept that planets like Earth ...

  6. History of Earth - Wikipedia

    en.wikipedia.org/wiki/History_of_Earth

    The first eon in Earth's history, the Hadean, begins with Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of Earth's crust and Earth itself.

  7. Timeline of first images of Earth from space - Wikipedia

    en.wikipedia.org/wiki/Timeline_of_first_images...

    First image, color images and movie of Earth from space taken by a person, by cosmonaut Gherman Titov – the first photographer from space. [25] [26] 1963 KH-7 Gambit: First high-resolution (sub-meter spatial resolution) satellite photography (classified). [27] 1964 Quill: First radar images of Earth from space, using a synthetic aperture ...

  8. The sun just did something weird, and 3 other space stories ...

    www.aol.com/news/sun-just-did-something-weird...

    Space is very big and quite often, very weird. Last week , an image captured by NASA's Reconnaissance Orbiter looked just like a bear, and "The Green Comet" reached its closest point to Earth in ...

  9. Pale Blue Dot (book) - Wikipedia

    en.wikipedia.org/wiki/Pale_Blue_Dot_(book)

    The first part of the book examines the claims made throughout history that Earth and the human species are unique. Sagan proposes two reasons for the persistence of the idea of a geocentric, or Earth-centered universe: human pride in our existence, and the threat of torturing those who dissented from it, particularly during the time of the Roman Inquisition.